Just a guess, I suspect two different Microsoft accounts have desynchronised. There are at least 3 different login/account mechanisms in Windows:
- For corporate use, accounts are managed centrally over the local network using a tool called Active Directory.
- Stand-alone passwords allow access to the computer when it isn't connected to a network. This is the classic mechanism.
- More recently, Microsoft Accounts linking the computer with remote Internet Cloud services like OneDrive. The idea is that one Account, the Cloud account, controls access to all Microsoft services, whether local or in the cloud. Local accounts still exist but they are managed by the Microsoft Account. Microsoft are pushing this method; rather than earn money by selling operating systems, they earn money by selling cloud services. The Microsoft Account is accessed by a single password, and it makes where services are delivered from transparent: could be on the host machine, or on the internet, or both.
As Active Directory is unlikely to be used in a Home Computer setup, I think Gary's Microsoft Account has become misaligned with a local account on his computer, probably due to a glitch caused by the update. Both Local and Microsoft Cloud Accounts complain when an old password is reused, so either of them could be rejecting the duplicate. Try changing to a completely new password.
Odd behaviours can often be fixed by rebooting the computer, hence the classic advice to 'turn it off and on again'. It clears out memory and resets everything to sensible defaults. But I don't think it would help here.
Dave
Edited By SillyOldDuffer on 16/05/2021 15:32:20